Rank Scores

Problem Statement

Table: Scores

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| id          | int     |
| score       | decimal |
+-------------+---------+
id is the primary key (column with unique values) for this table.
Each row of this table contains the score of a game. Score is a floating point value with two decimal places.

Write a solution to find the rank of the scores. The ranking should be calculated according to the following rules:

The scores should be ranked from the highest to the lowest. If there is a tie between two scores, both should have the same ranking. After a tie, the next ranking number should be the next consecutive integer value. In other words, there should be no holes between ranks. Return the result table ordered by score in descending order.

The result format is in the following example.

Examples

Example 1:

Input: 
Scores table:
+----+-------+
| id | score |
+----+-------+
| 1  | 3.50  |
| 2  | 3.65  |
| 3  | 4.00  |
| 4  | 3.85  |
| 5  | 4.00  |
| 6  | 3.65  |
+----+-------+
Output: 
+-------+------+
| score | rank |
+-------+------+
| 4.00  | 1    |
| 4.00  | 1    |
| 3.85  | 2    |
| 3.65  | 3    |
| 3.65  | 3    |
| 3.50  | 4    |
+-------+------+

Solution

Approach

• Use the rank method with method='dense' to assign ranks to the scores in descending order while handling ties. Add a new column 'rank' to the scores DataFrame to store the ranks.
• Sort the DataFrame by score in descending order. This can be achieved using the sort_values method.

Implementation

Using panda

import pandas as pd

def order_scores(scores: pd.DataFrame) -> pd.DataFrame:
    # Use the rank method to assign ranks to the scores in descending order with no gaps
    scores['rank'] = scores['score'].rank(method='dense', ascending=False)
    
    # Drop id column & Sort the DataFrame by score in descending order
    result_df = scores.drop('id',axis=1).sort_values(by='score', ascending=False)
    
    return result_df

Using MYSQL

SELECT
  Score,
  (SELECT count(*) FROM (SELECT distinct Score s FROM Scores) tmp WHERE s >= Score) Rank
FROM Scores
ORDER BY Score desc